Freeze drying is a well known process used to prepare storage stable compositions of pharmaceutical compounds which otherwise suffer degradation when stored in the presence of water, for example, because of disproportionation and/or hydrolysis. Examples of such pharmaceutical compounds include nucleotides. The problem is that freeze drying does not remove all the water from a composition containing such a pharmaceutical compound. The water which remains after freeze drying may destabilise the composition during storage.
Accordingly there is a need for compositions of pharmaceutical compounds such as nucleotides which when freeze dried are stable to long term storage.